Targeted deep brain stimulation reduces OCD symptoms
The debilitating behaviours and all-consuming thoughts, which affect people with severe obsessive compulsive disorder (OCD), could be significantly improved with targeted deep brain stimulation, according to the findings of a new collaborative study by researchers including a team from the University of Hertfordshire.
OCD is characterised by unwanted intrusive thoughts (obsessions) and repetitive stereotyped behaviours (compulsions- sometimes called rituals) and often means everyday activities become impossible for those with the condition. This repetitive and compulsive behaviour is commonly associated with either depressed mood or impairment in cognitive flexibility – an inability to flexibly adapt to changing situations.
Deep brain stimulation (DBS) is an emerging treatment for a small number of people with extremely severe OCD who have not responded to available treatment, such as cognitive behavioural therapy or medication. It requires neurosurgical implantation of electrodes.
In a study published today in Biological Psychiatry, six patients with treatment-refractory OCD were recruited from NHS England Highly Specialised OCD Services.
As part of the study, in a double-blind cross over trial*, each patient received DBS stimulation to brain areas previously associated with OCD, the anteromedial subthalamic nucleus (amSTN) for three months and DBS stimulation to the ventral capsule/ventral striatal area (VC/VS) for three months, followed by DBS stimulation to both amSTN and VC/VS. The neurosurgery and clinical assessments were carried out at the Unit of Functional Neurosurgery and Hughlings Jackson Ward, The National Hospital for Neurology and Neurosurgery, Queen Square, London (part of UCLH).
The study found that DBS at each site significantly and equivalently reduced OCD symptoms. However amSTN but not VC/VS DBS significantly improved cognitive flexibility, but VC/VS DBS had a greater positive effect on depressed mood.
Furthermore, MRI tractography (a form of brain imaging) from optimally activated electrode contacts showed that the two DBS sites affected different neural circuits within the brain. This finding provides clues as to the roles that those specific brain regions play in OCD, and has potentially important implications for treatment.
This is the first study to compare directly the effects of deep brain stimulation at two brain sites and has discovered important information about how the brain changes in severe OCD responsible for obsessions and compulsions, depressed mood and cognitive inflexibility might be alleviated.
Consultant Psychiatrist at the University of Hertfordshire
The finding that amSTN but not VC/VS DBS improved cognitive flexibility and that the effect of DBS on mood was significantly greater for VC/VS DBS, implicates the involvement of different neural circuitries associated with distinct symptoms in OCD. MRI tractography findings revealed that VC/VS and amSTN DBS modulate distinct brain networks implicated in OCD and are compatible with these clinical and cognitive observations.
Professor Eileen Joyce
UCL Queen Square Institute of Neurology
Cognitive flexibility was measured by the CANTAB IED test, and undertaken by researchers at Cambridge University. Their previous studies have shown that impaired cognitive flexibility is a marker of OCD and improvement implies that patients can break out of maladaptive routines and habits and take on new and rewarding experiences.
All patients had been ill for at least 20 years and failed to respond to high doses of medication plus intensive CBT. Patients were recruited from NHS England Specialised OCD Services, at South West London St George's Mental Health NHS and Hertfordshire NHS partnership. Additional patient expertise was provided by the Advanced Interventions Service at the University of Dundee and NHS Tayside.
The trials’ first patient was recruited in 2013 and the sixth and final patient finished the study in November 2016. The study was by funded by grants from the MRC and Wellcome Trust.
There are several limitations to the study, the main one being the small sample size. However, when comparing the effectiveness of the two DBS sites, patients served as their own controls in an innovative design, and the conclusions were robust to adjustment for multiple comparisons and parametric and non-parametric analyses. Nevertheless it would be important to test this hypothesis in a larger group of patients when the mechanistic actions of amSTN and VC/VS DBS on recovery from OCD can be evaluated in more detail.
*Double blind, means the researchers and patients did not know which target was being stimulated. Only the treatment providers, two neurologists, had this information. Crossover means the treatment was switched to the alternative area after a pre-determined period.
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